i wrote this explanation a while back may as well use it again.
Then you'll gain an understanding .
O-RILEYS Autos - This is the answer everyone gets here : saves us a lot of time ..and puts you quickly in the know.
You either go along with this or you're at the mercy of a garage that will charge you hundreds
Watch
O-RILEYS Autos on youtube ..he mainly does DPFs and mainly Transits, there is nothing he cant solve -- he takes you through it step by step ..watch maybe 4 or 5 videos and you'll have the knowledge
You must have plug in diagnostic scanner though ..or you just cant do it ..
They recommend "Forscan" which is free software that you download to a laptop..you buy the interface cable
You must join the forscan forum ..again free, to get the software and more answers.
https://forscan.org/forum/To give you some knowledgeThe mentoring system has two pressure sensors one before the DPF and one after.
The one after will be reading a little greater than atmospheric pressure, when running, the one before will be a bit greater than that one .. when you have a brand new DPF because of a little bit of back pressure from the core.
As the DPF gets full of soot,, the sensor "before" measures a greater pressure.than the one after. the program in the ecu calculates what the difference is between both sides. as a percentage.
The program knows when the difference between one side and the other exceeds certain values ..it then activates the DPF regeneration.
if the difference is beyond when this can happen, it puts up a fault code . it will probably lead to check engine light and limited acceleration.
Failed regeneration's can be caused by
vaporiser blockage..too many short trips or a DPF that is totally blocked... the vaporiser is as fuel injector type device that squirts neat diesel into or before the DPF ..it raises the temperature so that soot is burnt off .
There is also a temperature monitor ..so the ecu knows it is regenerating or if this has failed to happen or if its at too higher temperature ..in which case it shuts down the process, to stop it damaging the DPF .. leading to more codes and errors.
As mentioned watch Videos on youtube by "O'Riley's autos" he tells you how to get around all problems with DPFs , shows you cleaning methods and shows you how to interoperate what your scanner is showing ..how to force regeneration ..the pitfalls, the do's and the don'ts .
Diagrams of typical systems will be found with a google search.
all the best.mark